Oilseeds and fats, crops and lipids (Jan 2019)
Benefits of natural dietary trans fatty acids towards inflammation, obesity and type 2 diabetes: defining the n-7 trans fatty acid family☆
Abstract
Natural trans fatty acids are trans fatty acids that naturally occur in ruminant-derived foods: milk (derived from cow, ewe, goat), dairy products (yoghurt, cheese) and ruminant meat (beef, lamb). Because natural trans fatty acids are part of the trans fatty acid family, they have been compared for decades to their industrial counterparts on a cardiovascular outcome’s basis. At current dietary intakes, it is now well recognized that natural trans fatty acids are neutral towards cardiovascular health. Still, the negative connotation remains. It is usually taken for granted in the scientific community that natural trans fatty acids have no known physiological function and therefore no particular nutritional interest. This prevailing view has totally hidden several studies, which pointed out unsuspected benefits of natural trans fatty acids on inflammation, type 2 diabetes and obesity. Some supplementation studies dealt with pure trans-vaccenic acid (trans-C18:1 n-7) and pure rumenic acid (cis-9, trans-11 C18:2), but remained somewhat aside as they were carried out on rodents. However, recent epidemiological data reached considerable impact, highlighting a protective effect of trans-palmitoleic acid (trans-C16:1 n-7) towards the risk of type 2 diabetes. Bearing in mind that natural trans fatty acids do not just consist of rumenic acid, this review is the opportunity to sum up scientific knowledge about each of these three fatty acids. We shall therefore, review their occurrence in foods, and their physiological impacts. An overlooked aspect of natural trans fatty acids is that they are metabolically connected. The second aim of this review is to underline these metabolic connections. In fact, combining physiological impacts and metabolic pathways unravel shared mechanisms of action of trans-palmitoleic, trans-vaccenic and rumenic acids, that might be explained by their common n-7 trans double bond.
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